The invention relates to a cutter for removing tissue, with a cutter head, with a cutter shank which carries the cutter head and to which the cutter head is connected in a rotationally fixed manner, and with a drive driving the cutter shank.
Cutters of the previously known type are known in surgery. They are used in order to remove bony or cartilaginous tissue. The cutter head therein may be arranged eccentric to the cutter shank. It is consequently achieved that the cutter head with each revolution projects radially outwards over a defined angular path beyond a stationary sleeve or a stationary shank and may remove tissue.
With such cutters there arises, however, an unbalanced mass which is not insignificant and which impedes the machining accuracy. Furthermore, the effective active regions of the cutter are very difficult to determine accurately so that, inasmuch as this is concerned, the accuracy of the tissue removal is limited.
It is therefore the object of the invention to develop further a cutter of the initially mentioned type, such that the safety and the accuracy with its use is increased and the tissue removal may be effected with an increased precision. Furthermore, the efficiency of the removal is to be increased and the working rangexe2x80x94exactly adjustablexe2x80x94is to be increased.
For achieving this object the cutter according to the invention is characterized by a first rotatable sleeve which comprises an inner bore which is arranged eccentrically to the middle axis of this sleeve, and by a second stationary sleeve which is arranged in the inner bore of the first sleeve and which for the passage of the cutter shank comprises an inner bore which is arranged eccentrically to the middle axis of the second sleeve.
The arrangement of two sleeves, each with an eccentric bore, for the radial mounting of the cutter shank is achieved in a simple manner in that, by rotation of the two sleeves relative to one another, the cutter head with respect to its radial projection beyond the outer circumference of the outer sleeve may be adjusted simply and continuously in an exact manner. The effective effect of the cutter head with the removal of tissue may thus be exactly adjusted.
The handling of the cutter is simplified in that the second sleeve is connected to the drive or its housing in a rotationally fixed manner. Furthermore, the first sleeve is preferably connected in a rotationally fixed manner to a rotatable handle. With the latter, the effective eccentricity of the cutter head may be simply adjusted.
Furthermore, the eccentricity of the inner bore of the first sleeve and the eccentricity of the inner bore of the second sleeve are equally large. It is consequently achieved that, by way of a suitable rotation of the two sleeves relative to one another or of the first sleeve relative to the second stationary sleeve, the eccentric projection of the cutter head may be adjusted from zero up to a maximum value.
Preferably, the second sleeve with its outer diameter is arranged in the inner bore of the first sleeve with a clearance fit. Furthermore, between the outer diameter of the second sleeve and the inner bore of the first sleeve there may be arranged a sliding bearing, or this region may be designed as a sliding bearing.
With regard to manufacturing and assembly technology, there results a simple embodiment when the cutter head and the cutter shank are formed as one piece. Furthermore, the cutter shank may be connected to the drive shaft by way of a positive-fit connection. Finally, the cutter shank may be connected to the drive shaft further by way of a snap connection.
For reducing the weight of the cutter, the first and/or the second sleeve is essentially designed as a solid component only in the region neighboring the cutter head, and in the region neighboring the drive as a hollow component.